A rail, in the context of camera support, is a straight or curved length of track laid on a surface along which a camera dolly or slider travels to produce smooth, controlled linear or curved camera movement. Rails provide the guiding path that allows camera movement to be perfectly straight, repeatable, and free of the wobble or drift that hand-pushed movement on flat surfaces introduces.

Camera rails are typically made from aluminum or steel and come in sections that can be joined together to create runs of any required length. Standard dolly rails are wider than slider rails, designed to support the weight of a full camera dolly, tripod head, and operator. Curved rail sections allow the camera to travel along an arc rather than a straight line, enabling curved dolly moves and orbital paths around subjects. Rails are laid flat on the ground or on leveling legs for uneven surfaces, and the height and angle of the rail run can be adjusted to allow the dolly to travel up or down a slope. On major productions, laying, leveling, and adjusting the dolly rails is the dedicated responsibility of the grip department, and complex rail systems can take significant time to prepare. Smaller slider rails are compact enough for single-operator use and are frequently used on documentary, commercial, and independent productions. The visual signature of rail-based camera movement is its perfectly smooth, linear quality, free of the micro-vibrations that even gimbal-stabilized handheld movement retains.

In AI video generation prompts, describing the visual result of rail-based movement, such as "smooth linear camera track to the left," "fluid forward dolly along a straight path," or "smooth lateral camera slide," communicates the movement quality without requiring equipment terminology.